1. Title of Invention
The present invention relates to a highly wear-resistant aluminum-based composite alloy, more particularly to application of a quasi-crystalline aluminum-based alloy, which has the features of high strength and hardness, to applications where wear resistance is required. The present invention also relates to wear-resistant aluminum-alloy parts having improved compatibility with steel materials.
2. Description of Related Art
Heretofore, the high-strength aluminum-based alloys have been produced by means of the rapid cooling and solidification methods, such as the melt-quenching method.
Particularly, the aluminum-based alloy produced by the rapid cooling and solidification method disclosed in Japanese Unexamined Patent Publication Hei 1-275,732 is amorphous or fine crystalline. The fine crystalline alloy disclosed specifically in this publication is composed of an aluminum solid-solution matrix, fine crystalline aluminum matrix, and stable or meta-stable intermetallic compounds.
The aluminum-based alloy disclosed in Japanese Unexamined Patent Publication Hei 1-275,732 is a high-strength alloy which has high hardness of from approximately Hv 200 to 1000, and tensile strength of from 87 to 103 kg/mm.sup.2. The heat resistance is also improved since the crystallizing temperature is as high as 400K or higher. Furthermore, super-plasticity appears in this alloy at a high temperature where the fine crystalline phase is stable. The workability of this material is, therefore, satisfactory when its high strength is taken into consideration.
However, when the above mentioned aluminum-based alloy is exposed in a temperature region of 573K or more, the excellent properties of the material attained by the rapid cooling and solidification are impaired. There remains, therefore, room for improving the heat resistance, particularly the strength at high temperature. In addition, since the elements having relatively high specific gravity, such as Fe, Ni, misch metal and the like, are added up to 10 atomic % in the alloy of the above publication, there is no appreciable increase in specific strength. Furthermore, the high ratio of volume of the intermetallic compounds renders the ductility to be poor. Particularly, improvement of the elongation is required.
When the Al--Mn--Ce based aluminum-based alloy produced by the single-roll melt quenching method contains a solute element at a content exceeding a certain level, an fcc-Al solid solution plus icosahedral quasi-crystals are formed, and the tensile strength becomes as exceedingly high as from 535 to 1200 MPa (Seminar of Japan Society for Metals on 1993 "Nano-scale Structure Controlled Materials" (page 63) published Jan. 25, 1993).
The excellent wear resistance of the wear-resistant aluminum alloys known heretofore, i.e., the eutectic or hyper-eutectic Al--Si alloys, is attributable to the primary or eutectic Si dispersing structure in the Al matrix. However, since the coarseness of the primary Si crystals of the cast alloy is a few tens .mu.m or more, the cast alloy is difficult to re-form, and even the casting itself is difficult. Not only such production problems but also the sliding problems have been pointed out, that is, the coarse primary Si excessively roughens the surface of the opposed material.
It is also known that the atomized Al-35% Si alloy, primary Si of which is finely dispersed due to rapid cooling, is subsequently worked by the powder-metallurgy method. The wear resistance of the powder alloy produced by this method is itself improved but wears off the opposed material greatly. In addition, since the powder alloy is brittle and of low strength, its use in wear-resistant parts exposed to heavy load is difficult.